Our previous work unveiled a new mechanism linking vascularization and immunosuppression in human and mouse ovarian cancer: CD45+CD11c+CCR6+ dendritic cell precursors are massively recruited by beta-defensins to the tumor microenvironment, where they are transformed by VEGF in vivo into endothelial-like cells, termed Vascular Leukocytes (VLCs). VLCs represent the gateway for transmigrating anti-tumor lymphocytes and therefore emerge as critical orchestrators of immune tolerance in the ovarian cancer microenvironment. The central hypothesis of this project is that the aberrant gene expression profile of CD11c+ VLCs that infiltrate ovarian tumors can be specifically modulated in situ to re-program them to abandon their pro-angiogenic phenotype while inducing a therapeutically significant anti-tumor immune response. We have selected VLCs as the most frequent leukocyte subset infiltrating mouse and human solid ovarian carcinoma specimens. We hypothesize that VLCs, as non-dividing cells, will allow a much more durable effect of gene silencing or expression than the mere addition of recombinant cytokines. In Specific Aim-1, we will first define the optimal nanocarrier for the delivering functional nucleic acids (expression plasmid DNA or siRNA) to ovarian cancer-infiltrating VLCs, using contrasted nanocarriers tested in our lab as a starting point. We will then focus on two complementary approaches: Specific Aim-2 will determine the mechanisms of anti-tumor activity induced by the transfer of immunostimulatory genes to VLCs in the tumor microenvironment. Specific Aim-3 will investigate the feasibility and effects of VLC-specific silencing of immunosuppressive genes through siRNA. To accomplish these aims, we have assembled a multidisciplinary team combining expertise in nanotechnology and tumor immunology. Our results will establish the feasibility of regulating the aberrant expression of critical genes in the ovarian cancer microenvironment as a novel cancer intervention, which will pave the way for novel "nanotherapies" that may be also applicable to other solid tumors. PUBLIC HEALTH RELEVANCE: The accomplishment of these Aims will demonstrate the feasibility of regulating the aberrant expression of critical genes in the ovarian cancer microenvironment as a novel cancer intervention. This work will pave the way for a new generation of combinatorial treatments that will complement the classical "surgical debulking/chemotherapy" approach by targeting immunosuppressive and pro-angiogenic elements in the tumor microenvironment. Our results will also contribute to establish the use of nanocomposites for utilizing patients'own immune systems to prevent the recurrence and metastasis of cancers and provide a starting point for developing tools for cancer "nanotherapy", which may be also applicable to other solid tumors.